1 Answer

Palkia
Good, except you got the EVs wrong. There's no point to put EVs in Attack, you don't have any Physical moves. Instead put them in Speed, and the remaining ones put in Def.

Rayquaza
Great, but I would change Dragon Claw over Outrage due to it not making you confused.

Giratina
If you put EVs into SpAttttack and no EVs in Attack, why give him three attacking moves?

Keep the same EVs, and go with this moveset
-Aura Sphere
-Earth Power
-Dragon Pulse
-Shadow Ball
Aura Sphere covers Dark and Ice weakness, Dragon Pulse and Shadow Ball are STAB, and Earth power is coverage

Reshiram
Dragon Pulse over Outrage, due to its higher Sp Attack. Change Draco Meteor to Psychic, since you already got Dragon Pulse as STAB. Also, you can change Solar Beam into Hidden Power[Grass] for quicker damage.

Dialga@Admant Orb
Ability: Pressure
Nature: Timid
EVs: 252 SpAtt/ 128 HP/ 128 SpDef
-Roar of Time
-Earth Power
-Aura Sphere
-Flash Cannon
Flash Cannon and Roar of Time are STAB, Aura Sphere deals with Steel and Ice types, and Earth Power is some more coverage.